METABOLISM OF PESTICIDES 
Information concerning the fate of pesticides after application 
in the environment is useful to research workers who are concerned 
with their safe and effective use. It is important to know whether a 
compound will persist or whether it will be inactivated. Frequently, 
persistence is desirable for sustained control; for many uses, however, 
rapid detoxification of the compound may be desirable to avoid cumulative 
effects. 
Disappearance of pesticides takes place by leaching, volatilization, 
adsorption, decomposition, or metabolism; and the use to which a parti- 
cular pesticide is best suited may depend on the effects of one or more 
of these processes. 
This review is primarily concerned with the metabolism and decompo- 
sition of pesticides. The importance of these processes is apparent upon 
consideration of the facts (1) that the duration of toxic action can be 
related to the rate and manner in which the compound is metabolized; 
(2) that the rate of elimination from the body is dependent upon the 
physico-chemical properties of the metabolic products; (3) that the ability 
of a compound to reach a site of action may be limited by the rate at 
Which it is metabolized and the character of the metabolic products; and 
(4) that the toxicity of a compound can be decreased or intensified upon 
conversion to a metabolite. These points indicate the importance of 
knowing the pathways of metabolism as well as the degree of accumulation 
of metabolic products in tissue. From a more practical standpoint, the 
identification and measurement of residue levels of pesticides and their 
metabolites is necessary in order to fully evaluate the effects of pest 
control programs on wildlife. 
Metabolic pathways can be classified into seven groups that cover 
the majority of biotransformations which pesticides undergo. These are: 
1. Oxidation (in the sense that oxygen, as hydroxyl, takes 
part or is postulated to take part in one or more of the 
steps). 
(a) Hydroxylation of aromatic rings 
(b) Oxidation of side chains to alcohols, ketones, 
or carboxyl groups 
(c) Dealkylation from oxygen or sulfur (ether cleavage) 
(d) Sulfoxide formation 
(e) N-oxide formation 
15 

